As described in publication 1, MEMS (Micro Electro Mechanical Systems) are devices into which a variety of mechanical, electronic, optical, chemical, and other functions are integrated by semiconductor micro fabrication technology (semiconductor processing) or the like.
Currently, the MEMS are used to develop microswitches (switches in micro size) using an electrostatic actuator.
One example of such a microswitch is disclosed in publication 2. FIGS. 31(a) and 31(b) are explanatory diagrams illustrating the switch of publication 2.
As shown in FIGS. 31(a) and 31(b), the microswitch has a seesaw-like structure. In the microswitch, a rocking plate 81 is provided at the center of a beam (supporting leg) 84, which is provided in a column 80. The rocking plate 81 has a narrow-plate shape, and is provided with electrodes respectively at both ends.
On such parts of the substrate as to respectively oppose both ends of the rocking plate 81, adsorption electrodes (electrostatic force applying electrodes) 82 and substrate contact points 83 are provided. When an electric field is applied to one of the adsorption electrodes 82, the rocking plate 81 is attracted to the substrate. In this way, switching operation for connecting one of the electrodes of the rocking plate 81 and one of the substrate contact points 83 is performed.
Thus, the seesaw-like structure of the microswitch allows for driving the rocking plate 81 at a low voltage.
Publication 1: “Current Situation of MEMS Technology and Its Problems”, Technology Evaluation and Research Report (Technology Trend), No. 3 (published on Mar. 28, 2003 by Ministry of Economy, Trade, and Industry, Industrial Science And Technology Policy and Environment Bureau, Technology Evaluation and Research Division, Manufacturing Industries Bureau, Industrial Machinery Division)
Publication 2: Japanese Publication for Unexamined Patent Application, Tokukai 2002-287045 (publication date: Oct. 3, 2002)
However, according to the microswitch of publication 2, the rocking plate 81 (which has a narrow-plate shape) must perform up-and-down movement, using the beam 84 as an axis of rotation. Therefore, the beam 84 must have a small diameter. This means that the strength of the beam 84 cannot be increased.
As a result, the microswitch has a drawback that, since the beam 84 is fragile, the life of the microswitch is short.